Device for cooling electric machines, particularly turbogenerators

ABSTRACT

To cool turbogenerators having water-cooled stator and rotor windings and a cooling-water connecting head at the end of the rotor shaft, an intermediate tank containing a gas cushion maintained at a pressure slightly higher than atmospheric is interposed between a main water tank that is at elevated pressure and a water chamber that is at reduced pressure and is located adjacent a cooling-water discharge chamber. Water accumulating in the intermediate tank is fed back to the main water tank by a booster pump.

United States Patent Lambrecht et al.

[451 Sept. 17, 1974 1 DEVICE FOR COOLING ELECTRIC PrimaryExaminer-Charles Sukalo MACHINES, PARTICULARLY Attorney, Agent, orFirm-Herbert L. Lerner TURBOGENERATORS [75] Inventors: DietrichLambrecht; Erich [57] ABSTRACT Weghaupt, both of Mulheim, To coolturbogenerators having water-cooled stator Germany and rotor windingsand a cooling-water connecting head at the end of the rotor shaft, anintermediate [73] Asblgnee' '1;. lrmellgeseuschaft tank containing a gascushion maintained at a pressure u elm u jcrmmy slightly higher thanatmospheric is interposed between I22] Filed: Feb. 20, 1973 a main watertank that is at elevated pressure and a water Chamber that is at reducedpressure and is lo- [21] a, M cated adjacent a cooling-water dischargechamber. Water accumulating in the intermediate tank is fed [52] U.S.Cl. 165/47, 165/80 back to the main water tank y a booster p p- [51]Int. Cl. F24h 3/00 [58] Field of Search 165/47, 80; 310/54 WW V H V 5Claims, 1 Drawin F [56] References Cited g UNITED STATES PATENTS2,970,232 l/l96l Kilbourne 3lO/54 DEVICE FOR COOLING ELECTRIC MACHINES,PARTICULARLY TURBOGENERATORS The invention of the instant applicationrelates to a device for cooling electric machines, particularlyturbogenerators, and more specifically to such machines havingwater-cooled stator and rotor windings. Such a cooling device is known,for example, from German Published Non-prosecuted Pat. Application DOS 2016 169. In this heretofore known device, a cooling-water connectinghead is mounted on the end of the rotor shaft, and includes a shaft pumpdriven by the shaft as well as cooling-water input and output chambers.Moreover, in the circulatory loop between the coolingwater chambers,there is connected a water tank which is subjected to a cushion of gasacting at elevated pressure.

The following problems generally arise with a cooling-water circulationsystem of this heretofore known type: first, the pump should have aself-contained drive, which is generally achieved by directly couplingthe pump to the rotor. In addition, attention must be given to operatingthe cooling-water pump with minimal cavitation. Wear due to cavitationat the intake of the shaft pump increases, however, with increasingrotary speed and increasing water flow rate. In order to avoid excessivewear due to cavitation at the pump, an initial or prior pressure isrequired in the suction line, which can be 3 to 4 atmg (atmospheresexcess pressure), depending upon the operating rotary speed and thewater flow rate. This pressure is usually generated by a gas cushionintroduced into the water tank. This entire gas cushion pressure,however, also acts on the outermost water chamber at the cooling-waterconnecting head that faces toward atmosphere, so that an undesirablyhigh pressure occurs at the shaft seal.

To seal the shaft, a maintenance-free and wearresistant seal thatfulfills the requirement for turbogenerator design of a running time ofat least 20,000 hours without stopping, is accordingly necessary.Contactfree slotted or split sleeve seals or labyrinth-type seals havebeen found to be most reliable and suitable, as they are also leastcostly from the technical standpoint. With such contact-free slotted orsplit sleeve seals, continuous water-leakage on the air side isunavoidable. This water leakage should, however, be kept as low aspossible. Since this leakage water is chemically pure and accordinglyhas low electrical conductivity, the recovery or reclamation thereof inthe course of continuous operation cannot be disregarded. This leakagewater becomes enriched with oxygen, however, when in contact with air,which can cause corrosion in the conventionally hollow lines or passageslocated in the rotor and stator windings. Consequently, the leakagewater is conducted through a collecting tank and over a palladiumcatalyzer wherein the oxygen entrained by the leakage water combineswith the hydrogen therein to form additional water which is thenreturned to the main water tank. The necessity for keeping the waterleakage as low as possible is dictated by the fact that the size of theultraexpensive palladium catalyzer increases in proportion to the waterflow rate.

It is accordingly an object of the invention to provide a device forcooling electric machines which has a cooling-water circulatory systemwith a water connecting head that has the least possible water leakage.Since the required suction pressure and, accordingly, the starting orprior pressure in the water tank must be maintained,

on the one hand, for operating the pump with minimal cavitation, while,on the other hand, the amount of water leakage is dependent upon thepressure in the end-most water chamber at the air side, a further objectof the invention is to provide means for markedly reducing this pressurewithout, however, sacrificing the integrity of the closed circulatoryloop.

With the foregoing and other objects in view, there is provided inaccordance with the invention, a device for cooling electric machines,particularly turbogenerators, having a rotor mounted on a shaft andwatercooled stator and rotor windings, comprising a coolingwaterconnecting head located at an end of the rotor shaft and having acooling-water inlet chamber and a cooling-water outlet chamber,circulatory means interconnecting the inlet and outlet chambers, anexternal water tank connected in the circulatory means between the inletand outlet chambers, means for maintaining a gas cushion at elevatedpressure within the external water tank, a pressure-reducing waterchamber located adjacent and communicating with the outlet chamber, anintermediate tank connected between the pressurereducing water chamberand the external water tank and having an air cushion therein at apressure slightly higher than atmospheric pressure, and booster pumpmeans connected between the intermediate tank and the external watertank for recirculating water accumulating in the intermediate tank tothe external water tank.

By means of this provision of an intermediate tank and thepressure-reducing effect thereof at the endmost sealing location of thecooling-water connecting head, the water leakage occurring at the airside of the connecting head is reduced to a minimum. Accordingly, it ispossible also to employ a slotted or split sleeve seal at this locationindependently of the output of the machine and the operating rotaryspeed thereof. Due to this pressure reduction in the end-most waterchamber of the connecting head, the sealing problems, which would haveotherwise been difficult to solve and which result from theaforementioned lengthy running periods and from the axial expansion ofthe rotor shaft of about mm or more for large machines, are greatlyreduced.

In accordance with another feature of the invention, and in order tomaintain a predetermined pressure of the gas cushion in the intermediatetank, means are provided connecting the external water tank and theintermediate tank so as to afford communication between the respectivegas cushions therein, a safety valve being connected in the connectingmeans between the external water tank and the intermediate tank. Inaccordance with yet another feature of the invention, a safety valve isconnected to the intermediate tank.

Tapped water escaping nevertheless from the pressure-reducing waterchamber can be withdrawn in a conventional manner from a further chamberlocated, in accordance with yet another feature of the invention,adjacent the pressure-reducing water chamber and having a pair ofopposite walls having respective ends, between which and the rotorshaft, shaft sealing means are interposed, the shaft sealing meansadmitting into the further chamber atmospheric air in addition to thetapped water. The tapped water withdrawn from the further chamber isthen recirculated to the external water tank through circuit meansconnecting the further chamber with the external water tank andincluding a collecting tank, a pump and oxygenremoving catalyzer meansconnected therein.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin device for cooling electric machines, particularly turbogenerators,it is nevertheless not intended to be limited to the details shown,since various modifications and structural changes may be made thereinwithout departing from the spirit of the invention and within the scopeand range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the single FIGURE of the drawing which is adiagrammatic view of the device for cooling electric machines inaccordance with the invention, schematically showing the circulatorysystem for cooling water and the cooling-water connecting head.

Referring now to the drawing FIGURE, there is shown therein a centralcooling-water tank 1 wherein an initial or prior pressure of about 3atmg is maintained by a gas cushion 2. Cooling water flows from thecentral or main tank 1 through a suction line 3 into an inlet or suctionchamber 4 formed in a coolant-water connecting head 5. The cooling wateris fed from the inlet chamber 4 by a shaft pump 7, which is mounted onthe shaft 6 of an otherwise unillustrated electric machine such as aturbogenerator, through a line 8 and a cooler 9 to the schematicallyshown stator winding 10 of the machine and to an axial bore 11 formed inthe shaft 6 of the machine rotor for cooling the schematically shownrotor winding 12. The warmed cooling water then flows back from thestator winding 10 through a line 13 directly to the external water tank1 and from the cooling-water outlet chamber 14 in the cooling-waterconnecting head 5 out of the rotor and through a line 15 into theexternal water tank 1. The pressure in the cooling-water outlet chamber14 is about 3.5 atmg, so that this pressure also prevails at the slottedor split sleeve or labyrinth seal 16 between the outlet chamber 14 andan adjacent chamber 17. In accordance with the invention, the adjacentchamber 17 is connected by a line 18 with an intermediate tank 19wherein a pressure slightly above atmospheric pressure is maintained bya gas cushion 20, the pressure in the adjacent chamber 17 being from 350mm water column to about 0.2 atmg. In the additional adjacent chamber17, there prevails a pressure of 0.25 to about 0.4 atmg only, which isalso simultaneously applied to the slotted or split sleeve seal 21located at an end of the wall disposed between the water chamber 17 andthe nextsucceeding chamber 22. Due to this pressure reduction, thegreatest part of the leakage water discharged from the cooling-wateroutlet chamber 14 is delivered to the intermediate tank 19, withouthaving any connection to atmosphere, and only a relatively smallquantity of leakage water flows into the leakage water chamber 22 whichis partly filled with air and partly with hydrogen separated from thewater. The pressure of the gas cushion can then, in accordance with theinvention, be adjusted without regard to any other matters so that, onthe one hand, a minimal quantity of leakage water is obtained while, onthe other hand, however, a breakthrough of air from the chamber 22through the slotted or split sleeve seal 21 into the pressure-reducingadjacent chamber 17 under all operating conditions is avoided. Theleakage water then flows in conventional manner into a lower lyingcollecting tank 23 and is pumped back into the external water tankthrough a palladium catalyzer 26, regulated with the aid of a waterlevel control 24 and a return flow pump 25. The quantity of tapped waterflowing into the intermediate tank 19 is also regulated by a water levelcontrol 27 and is returned to the main water tank 1 with the aid of abooster or pressure-raising pump 28. The gas cushion 2 formed in themain water tank 1 through a hydrogen supply line 29 and apressure-reduction valve 30 is connected through anotherpressurereduction valve 31 with the gas cushion 20 formed in theintermediate tank 19. In addition, a safety valve 32 set to 0.1 to 0.2atmg ensures that the gas cushion pressure is not exceeded in theintermediate tank 19.

Accordingly, in a relatively simple manner, the aforedescribed device ofthe invention assures reliably and economically, that only a very smallamount of leakage water escapes from the cooling-water connecting headand is mixed with entering air. Moreover, due to the consequent pressurereduction, relatively simple slotted or split sleeve or labyrinth sealscan be employed at all sealing locations.

We claim:

1. In a system for cooling electric machines of the type having a rotormounted on a shaft and watercooled stator and rotor windings, comprisinga coolingwater connecting head located at an end of the rotor shaft andhaving a cooling-water inlet chamber and a cooling-water outlet chamber,circulatory means interconnecting said inlet and outlet chambers, anexternal water tank connected in said circulatory means between saidinlet and outlet chambers, and means for maintaining a gas cushion atelevated pressure within said external water tank: a pressure-reducingwater chamber located adjacent and communicating with said outletchamber, an intermediate tank connected between said pressure-reducingwater chamber and said external water tank and having an air cushiontherein at a pressure slightly higher than atmospheric pressure, andbooster pump means connected between said intermediate tank and saidexternal water tank for recirculating water accumulating in saidintermediate tank to said external water tank.

2. Device according to claim 1 including means connecting said externalwater tank and said intermediate tank so as to afford communicationbetween the respective gas cushions therein, and a pressure-reducingvalve connected in said connecting means between said external watertank and said intermediate tank.

3. Device according to claim 1 including a safety valve connected tosaid intermediate tank.

4. Device according to claim 1 including water-level control means forregulating outflow of water accumulated in said intermediate tank tosaid external water tank.

5. Device according to claim 1 including a further chamber adjacent saidpressure-reducing water chamber and having a pair of opposite walls,shaft sealing means disposed between respective ends of said walls andthe rotor shaft and being adapted to admit atmother chamber to saidexternal water tank, said circuit means including a collecting tank, apump and oxygenremoving catalyzer means connected therein.

UNITED STATES PATENT e-T FTQE CERTIFICATE OF CGRRECTION PATENT NO.3,835,9 9 DATED September 17, 1974 |NVENTOR(S) Dietrich Lambrecht, ErichWeghaupt It is certified that error appears in the ab0ve-identifiedpatent and that said Letters Patent are hereby corrected as shown below;

In the heading to the printed specification the priority information wasomitted. It should read as follows:

--Foreign Application Priority Data February 17 1972 Germany P 22 07342.3".

fiigned and ficalcd this A ttes t:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner of'ParenIsand Trademarks I UNITED STATES PATENT @Fl' lfifi CERTIFICATE OF CQREQHQPATENT NO. 3,835,919 DATED September 17, 197A |NVENTOR(S) DietrichLambrecht, Erich Weghaupt It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

In the heading to the printed specification the priority information wasomitted. It should read as follows:

--Foreign Application Priority Data February 17, 1972 Germany P 22 07 342.3".

inedi and caicd this twentieth D y 0F a y 9 [SEAL] Attest:

RUTH C. MASON Q. WAIRSHALL DANN Arresting Officer Commissioner ofParenrsand Trademarks

1. In a system for cooling electric machines of the type having a rotormounted on a shaft and water-cooled stator and rotor windings,comprising a cooling-water connecting head located at an end of therotor shaft and having a cooling-water inlet chamber and a cooling-wateroutlet chamber, circulatory means interconnecting said inlet and outletchambers, an external water tank connected in said circulatory meansbetween said inlet and outlet chambers, and means for maintaining a gascushion at elevated pressure within said external water tank: apressurereducing water chamber located adjacent and communicating withsaid outlet chamber, an intermediate tank connected between saidpressure-reducing water chamber and said external water tank and havingan air cushion therein at a pressure slightly higher than atmosphericpressure, and booster pump means connected between said intermediatetank and said external water tank for recirculating water accumulatingin said intermediate tank to said external water tank.
 2. Deviceaccording to claim 1 including means connecting said external water tankand said intermediate tank so as to afford communication between therespective gas cushions therein, and a pressure-reducing valve connectedin said connecting means between said external water tank and saidintermediate tank.
 3. Device according to claim 1 including a safetyvalve connected to said intermediate tank.
 4. Device according to claim1 including water-level control means for regulating outflow of wateraccumulated in said intermediate tank to said external water tank. 5.Device according to claim 1 including a further chamber adjacent saidpressure-reducing water chamber and having a pair of opposite walls,shaft sealing means disposed between respective ends of said walls andthe rotor shaft and being adapted to admit atmospheric air and watertapped from said outlet chamber into said further chamber, and circuitmeans connecting said further chamber and said external water tank forrecirculating the tapped water received in said further chamber to saidexternal water tank, said circuit means including a collecting tank, apump and oxygen-removing catalyzer means connected therein.